Generally, when an image forming apparatus is turned on, it initiates a warm-up cycle. During warm-up, various internal components such as a photosensitive drum or a cooling fan are powered on. For example, air from the room in which the image forming apparatus is located may be drawn inside the image forming apparatus by a fan. Simultaneously, a fixing unit may become operational. Both the fan and fixing unit generate heat once they begin to operate.
Depending on several environmental factors, dew may be present on the photosensitive drum at warm up. Generally, dew is the formation of moisture on cool surfaces. This is an undesirable condition because dew on the photosensitive drum may lead to ink smudging and the production of defective images during the reproduction of an image.
Generally, to eliminate dew formation on the photosensitive drum, a heater is provided that heats the photosensitive drum when the temperature inside the image forming apparatus is lower than the temperature outside the image forming apparatus.
In addition, a fan may be used to warm the drum. The fan is controlled by a system that detects the difference between the temperature inside and outside the image forming apparatus. When the temperature difference equals a certain value, the fan is turned on to warm the drum.
While this process is somewhat effective, it fails to take into account the humidity present inside the image forming apparatus. Humidity is the measure of water vapor in the air. Accordingly, humidity is a major factor relating to the formation of dew on the photosensitive drum.
The conditions necessary for dew to form on the photosensitive drum depend upon the surface temperature of the photosensitive drum and the internal temperature and humidity near the drum. Thus, whether dew will form on the photosensitive drum during warm-up is not accurately determined by relying solely on the difference in temperature inside and outside an image forming apparatus.
Accordingly, an accurate system is needed to predict whether dew will form on the photosensitive drum. Further, a system and method is needed to warm-up an image forming apparatus such that dew is not formed on the photosensitive drum after the image forming apparatus has completed its warm-up cycle.